Evolution and development of rooting structures

Question 1

early root type

Answer 1

1D roots, or ‘rhizoids’- coming straight out the bottom of the plant

ex- Chara braunii

Question 2

lycophyte roots

Answer 2

3D growth underground- get branching roots - ‘bifurcating’

Question 3

where do proper roots emerge

Answer 3

monilophytes- root apical cell (tetrahedral-ish), from which other cells emerge

Question 4

developmental zones of a root

Answer 4

meristem (quiescent centre, area of active division)
meristematic zone
elongation zone
differentiation zone

Question 5

how is RAM maintained

Answer 5

wox5 maintains stem cell identity and function
row1 restricts it to the quiescent centre

Question 6

columnella

Answer 6

under the columnella, divides (anticlinally) to make more rows and therefore extend out the root tip

Question 7

how is epidermis formed

Answer 7

anticlinal divisions forms epidermal cells- related to fez and sombrero (smb) function

Question 8

fez and sombrero

Answer 8

fez- promotes division, smb represses excessive division- feedback loop where SMB seems to downregulate FEZ, meaning there is no FEZ expression in differentiated cells

Question 9

formation of endoderm and cortex

Answer 9

anticlinal divisions again come from the same initial set of cells

genes- short root (shr), scarecrow (scr)

Question 10

scr and shr

Answer 10

need to watch the lecture but cannot pls come back to this

Question 11

lateral root formation

Answer 11

a lot of auxin regulation
important genes for this- slr, arf7 and ard19 which are required for initiation

Question 12

slr

Answer 12

very much required for lateral root formation

Question 13

arf7 and 19

Answer 13

also required for lateral root initiation, but slightly more redundancy- just get less of them if you take one away and leave the other

Question 14

PRH1

Answer 14

induces expander genes to make the lateral roots protrude

Question 15

root hair cell formation- spacing mechanism

Answer 15

form where there are 2 cortex cells touching it, which happens kinda periodically along the root- makes for spacing kinda naturally

Question 16

rsh2

Answer 16

necessary for initiation, conserved function with rhizoid development in more basal plants

Question 17

how do LRL genes work in bryophytes

Answer 17

auxin is needed to facilitate LRL1,2 genes

Question 18

how to LRL genes work in arabadopsis

Answer 18

LRL1 and 2 are independent, LRL3 needs auxin activation and has diff downstream stuff